On a desperate mission to save Planet Earth, Supergirl (Helen Slater), must
retrieve a missing life-giving power source to save her home city from total
destruction.

Startled by her own amazing Superpowers, Supergirl traces the lost Omegahedron
only to discover that it has fallen into the hands of the rapacious Selena (Faye
Dunaway) who unleashes untold horrors to thwart her young adversary. When Selena
ensnares her brave opponent in the dreaded Phantom Zone, it seems that
Supergirl's mission - and the Universe - are doomed...